1. Field of the Invention
The invention relates to a technology of lighting for assisting in photographing surroundings of a vehicle.
2. Description of the Background Art
A conventionally-known image display system is of a type installed in a vehicle such as a car, photographing surroundings of the vehicle and generating their images to display on a display in a cabin of the vehicle. For example, an area outside a front fender of the vehicle which is opposite to a driver seat is often a blind corner for a driver. By using an image display system that shows photographed images of the area outside the front fender, the driver can easily see clearance between a side of the vehicle body that is opposite to the driver seat and an object in a case of going by an oncoming car on a narrow road or the like.
However, in a dark surrounding environment, such as at night, light exposure is insufficient for such an image display system to take photographs so that images of the surroundings of the vehicle cannot be displayed with enough brightness. Therefore, Japanese Patent No. JP2004-189060 A discloses a technology for emitting auxiliary light to assist in photographing and lighting an area to be photographed in a relatively dark surrounding environment to ensure necessary brightness for satisfactory images.
Recently, a technology is required to display in a cabin of a vehicle not only images of a limited area surrounding the vehicle such as an area outside a front defender of the vehicle but also images of a wider area. For example, lateral areas of a vehicle are hard for a driver to see. Therefore, an image of an entire lateral area from a front space of a front end to a back space of a rear end of the vehicle is requested to be displayed in the cabin of the vehicle. For another example, as disclosed in WO Publication No. WO 00/07373 A1, in one of proposed technologies, surroundings of a vehicle are photographed by using multiple on-vehicle cameras and the photographed images are combined to generate a composite image viewed from an arbitrary virtual viewpoint such as from a top or a rear point of the vehicle, to provide the composite image to a driver.
Even in such a case where an image of a relatively wide area is displayed in a cabin of a vehicle, it is required to light an area surrounding the vehicle in a relatively dark surrounding environment. However, as an area to be photographed becomes larger, huge amounts of electricity is required to evenly and constantly light the entire area that needs lighting for photographing, which may lead to shorter durability of a light source providing light because of degradation of the light source.